Theory of industrial organization is not a brand-new field, and we have many papers on several industries. However, there are not so many papers on Japan's non-life insurance industry by using standard econometrics. We aim to make up for the gap and to adopt an orthodox econometrics into the industry.Although we have both the historical studies and the cross-sectional analysis using by econometrics, there are no the cross-sectional and time-series approach to the non-life insurance industry in Japan. In this research, we collected the post-war data as long as we could, and investigated the data of individual insurance company. And then we tried to understand the whole picture of the post-war non-life insurance industry. How to get the picture in this research are that we make a database which we called 'panel data', and examine the industrial organization using both the traditional statistical analysis and the orthodox econometrics.This research show the followings.1. Some characteristics of the post-war non-life insurance industry are made clear by econometrics using panel data.2. We get interesting results that could use in examining the strategy of each insurance company.3. After completed this research, we are possible to compare life insurance and non-life insurance industry. Both industries have been under regulations and supervision by the Ministry of finance long time.By the way, now in Japan, we met the drastic changes in the non-life insurance industry. We are in the era of transformation in insurance system, and it is naturally that the characteristics would be changing. In the near future, after adding data, we would like to reexamine the changes in the industrial organization. Results in this research are an important step to such a study.